2. Clays

2.1 Common features

The most common clays are phyllosilicates or smectites. Their main characteristic is that they have a crystalline structure in the form of nanometer-thick sheets (and therefore a high aspect ratio), which gives them a large specific surface area. Clays generally contain impurities such as quartz...

The classification of clays is defined by their crystalline structure, but also by the quantity and position of ions within the unit cell. The main classes range from kaolins, which have a uniform chemical composition, to smectites, which vary greatly in composition and cation exchange capacity. The spacing between individual layers is governed by the presence of cations in the interlayer space.

It should be noted that there...